You can quickly and easily made a slideshow in the Photos app, but those can't be exported to share. By using the free iMovie app from Apple, you can build a slideshow from a set of photos in minutes and then export it as video to share. You can also customize each photo with filters, cropping, movement and text. You can add music, audio and narration to the slideshow too. The basic idea works on the iPad as well.
Sometimes you need to shrink an image in order to upload it to a web site or send to someone. You can do this easily on a computer, but it is harder to do on an iPhone or iPad. This Shortcut will give you a way to do it by sharing the photo to create a smaller file.